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Abstract
Scrambling and descrambling systems serve in many important applications in
satellite transmissions. The need to restrict access on a subscriber –by–
subscriber basis to various channels available in cable TV systems or satellite
transmissions showed the need for scrambling.
Therefore, to prevent non-authorized access to one or more of satellite
transmitted channels, the operator employs a conditional access system for
scrambling and descrambling the actual television pictures within each of the
channels. The descrambler serves to descrambling operations of the scrambled
received audio/video signal.
The contribution of the present work can be summed up into two major points,
the analysis of the architecture of digital satellite TV receivers (DSTVRs) and the
development of a descrambler unit that can descramble scrambled video
broadcasted transmissions in an effort to develop and manufacture an Egyptianmade
DSTVR. The conditional access system inside DSTVRs was thoroughly
analyzed with its two main processes, the descrambling and the decryption
processes.
This thesis described two techniques for implementing a descrambler system for
DSTVRs. The first technique presented a descrambler system based on STi55xx
chipset; an application specific integrated circuit chipset family for complete
single-chip DSTVR based on ST20 processors. The second technique adopted the
implementation of the common scrambling algorithm; the algorithm used to
scramble DVB broadcasted streams; in high level programming language, as a
step towards the implementation of the algorithm on digital signal processors.
In the first technique, application software for DSTVRs is implemented in high
level programming language like ANSI C and is mapped to targets
hardware,STi55xx chips, using ST20 Embedded Toolset. This toolset has been
used to support application development for ST20-based systems.